1970 open face 55A alternator
 

Slowly working towards reinstalling the A/C on my 1970 Formula. While a lot of the system had been removed by the previous owner, he had carefully packed up and stored all the original brackets, compressor and condenser from the car. The one thing for sure that wasn’t there is the correct alternator. Not sure if the current unit is even 55A. For those who are familiar with rare & used parts I have several questions.

1) What would a 1100903 55 A alternator sell for? I realize that ultimately something is worth whatever somebody will pay and that Ebay skews values up, but I'm asking for a ballpark number that those in the know would think fair and reasonable.

2) How much of a unicorn is one of these? Are they something that at least pops up once in a blue moon or are they so scarce that "knowing a guy who knows a guy" is the only way you're ever likely to find one?

3) Aside from the proper cases, are there any other specific parts or telltales to look for that prove it's authentic and not just a Frankenstein?

4) If you couldn't find a real one, are the correct open front and proper rear casings out there to at least dress up a newer or different model Delcotron to appear correct?

As always, thanks in advance for any input or suggestions you care to make. Dennis

903
 

The 55 amp 903. Well Im.restoring my 1970 formula ra3 auto and it had alot of options. It was my dad's car and Im.getting things ready too. I am engine Trans number matching date coded rear end is a 307 cos 12 bolt that I'll run and if happy have it rebuilt and posi or change to 331 or 342 posi. My alternator suppose to be a 904 61 amp but I have never seen one but doing this quest I have collected a restamped 903, 1 real 903, 1 rebuilt 903 , 1 original 902, 1 damaged rebuilt 902, 2 blanks 1 a core 1 new. Cores are open face, and 2 open.face 928 and 2 700's and about 6 standard core plus 1 80 amp big boy for sd. I've seen originals 903 restored sell for 1500, last 902 restored I think sold for 1250. In last year only seen 1 restored 903 and was on ebay. They are expensive. I sent you pictures of my original 903, notice the stamp font and the Delco raised emblem close to.mounting hole in second picture. Restamped ones will blank ooen face front will not have this stamp. Im.not an expert I. It's my goal to restore my 1st car that was my father's back to.stock . I might just shelf this unit and run a custom blank I bought and put a 70 raised fin correct back and have it 61 amp. It's 75 now. I seen restored alternators with new fan and pully and they look good. Fans are silver in cor and pulley is gold. I've also learned that restoration price o. These depends on level your car will be. A concourse car will have a lot more expensive rebuilt alternator that a good driver. There is 1 nos 902 on ebay for 2k. I'm just sharing with you my experience with these alternators. Hope this helps you

903
 

The 55 amp 903. Well Im.restoring my 1970 formula ra3 auto and it had alot of options. It was my dad's car and Im.getting things ready too. I am engine Trans number matching date coded rear end is a 307 cos 12 bolt that I'll run and if happy have it rebuilt and posi or change to 331 or 342 posi. My alternator suppose to be a 904 61 amp but I have never seen one but doing this quest I have collected a restamped 903, 1 real 903, 1 rebuilt 903 , 1 original 902, 1 damaged rebuilt 902, 2 blanks 1 a core 1 new. Cores are open face, and 2 open.face 928 and 2 700's and about 6 standard core plus 1 80 amp big boy for sd. I've seen originals 903 restored sell for 1500, last 902 restored I think sold for 1250. In last year only seen 1 restored 903 and was on ebay. They are expensive. I sent you pictures of my original 903, notice the stamp font and the Delco raised emblem close to.mounting hole in second picture. Restamped ones will blank ooen face front will not have this stamp. Im.not an expert I. It's my goal to restore my 1st car that was my father's back to.stock . I might just shelf this unit and run a custom blank I bought and put a 70 raised fin correct back and have it 61 amp. It's 75 now. I seen restored alternators with new fan and pully and they look good. Fans are silver in color and pulley is gold. I've also learned that restoration price on these depends on level your car will be. A concourse car will have a lot more expensive rebuilt alternator that a good driver. There is 1 nos 902 on ebay for 2k. I'm just sharing with you my experience with these alternators. Hope this helps you

Thank you for this and the pics. Lots of good ID info to keep in mind.

A 903 55 amp alternator with correct back has a limited market. That said, its mostly cars with AC. Still sell well, but lots are now just flipper material, or swap meet vendors want a conversation piece.. yeah many do that.
IF you have it, and it looks the part, run it and look for a 904 . No need to collect stuff as the cars needing originals is Not going up in number .
With parts available today you can make ANY 10Si alternator have 75 to 130 amps.
There is no need for more than 61 amps, and that is only needed driving at night with ac on max.

Most of those rear cases were changed over the years as I have been told there were issues with that heat sink?Tom

my original 902 has a crack in the rear bolt boss;
I still have it, but I put it aside and swapped in a later rear case so that I could tighten the rear bolt.
I don't know if that's a common thing or not, but it might lend to clear up why the rear cases go MIA.

The front spokes crack near the middle..

I think I have 3 open face Alts here with the wrong backs.Tom

Depends if they are 902/903s or 927/928s. The 927/928s had the later rear case that did not have the raised fin area. Those rear cases are common.

Bean counters.. cost to make the replacement was I think 15 cents less, or something close..